In recent years, run flat tires including load support layers inside sidewalls have been developed and widespread. Highly hard crosslinked rubber is used for the support layers. Such run flat tires are called a side reinforcing type. In this type of a run flat tire, if the internal pressure is reduced due to puncture, a load is supported by the support layers. The support layers suppress flexure of the tire in a punctured state. Even if running is continued in the punctured state, the highly hard crosslinked rubber suppresses heat generation in the support layers. This run flat tire allows for running for some distance even in the punctured state. An automobile having such run flat tires mounted thereon need not be always equipped with a spare tire. The use of this run flat tire avoids change of a tire in an inconvenient place.
When running with the run flat tire in a punctured state is continued, deformation and restoration of the support layers are repeated. Due to the repetition, heat is generated in the support layers, and the temperature of the tire reaches a high temperature. The heat causes breakage of rubber components of the tire and separation among the rubber components of the tire. It is impossible to run with the tire in which the breakage and the separation have occurred. Run flat tires are desired which allow for running for a long period of time in a punctured state, in other words, run flat tires are desired in which breakage and separation due to heat are less likely to occur.
JP2009-298397 discloses a run flat tire having dimples on sidewalls thereof. The surface shape of each dimple is a circle. The surface area of each sidewall is large. In the tire, the dimples generate turbulent flow. The large surface area and the turbulent flow promote release of heat from each sidewall to the atmosphere. In the tire, the temperature is less likely to rise.
JP2010-274886 discloses a run flat tire having dimples whose surface shapes are elongated circles. In the tire as well, release of heat from each sidewall to the atmosphere is promoted by the dimples. The elongated circles have directionality. In the tire, heat release is further promoted by making the longitudinal direction of each dimple appropriate. In the tire, the temperature is less likely to rise. The tire is excellent in durability during running in a punctured state.